1. Field:
This invention is in the general field of mastitis detecting devices for use in the dairy industry and is particularly concerned with devices of this type that test electrical conductivity of milk secretions of the mammary glands of dairy cows.
2. State of the Art:
Various ways of testing dairy cows for the disease known as mastitis, which infects the mammary glands of a great many of the dairy cows being milked throughout the world, have been developed in the past. None of these have been entirely satisfactory. Viscosity testing of milk from each of the four quarters of the udder of a dairy cow is commonly used in the U.S.
Testing electrical conductivity of the milk has been tried experimentally in the U.S. and has been used in New Zealand. Infected quarters of an udder produce milk lower in lactose and higher in sodium chloride than quarters of an udder that are not infected, and electrical conductivity of such milk is not the same as that from non-infected quarters. Ordinarily, not all quarters of a dairy cow's udder are infected or infected to the same degree, so that comparing the electrical conductivity of milk taken sequentially from the four quarters provides a reasonably reliable indication of mastitis infection.
A conductivity test instrument which has achieved significant commercial success in New Zealand, where it was developed, is described in an article entitled "Method of Mastitis Detection Including the Rolling Ball Viscometer and Electrical Conductivity Meter" by Graham F. Doire appearing on pages 25-34 of the Proceedings of the 19th Annual Meeting of the National Mastitis Council Inc. held at Louisville, Ky., on Feb. 18-20, 1980. It provides for measuring conductivity of milk from the four quarters of a dairy cow's udder individually and in sequence and includes a switching system controlling the energizing of a green and red light, individually or together, to indicate relatively low, relatively high, and intermediate conductivity measurements, respectively. The four readings are recorded by an observer and compared to establish a positive or negative condition for each quarter.
Although this New Zealand device has the advantages of being relatively inexpensive and easily operated by a dairyman at cowside, with more easily and more quickly interpretable results than had been possible theretofore, it requires a second person to be present to record the results of each quarter testing and does not provide adequately for differences in herd type, particular stages of lactation, or individual cow chemistry.
Further, in use, milk is introduced into a closed-bottom conductivity cell, the measurement taken, and then the cell turned upsidedown to empty the milk before another sample of milk is placed in the cell for testing. It has been found with such a device that milk remains on the sides of the cell after the sample is poured out, so that, after several readings have been taken, the samples become contaminated and the cell has to be cleaned before further use. Ideally, the cell should be cleaned after every use.
In the U.S., where testing has been done regarding the relationship between conductivity readings and the presence of mastitis, the tests have all been experimental using laboratory bench-type conductivity meters. Again, such meters have closed-bottom conductivity cells to hold the samples of milk being tested or prong-like conductivity cells which are inserted into closed-bottom containers holding the samples, and in both cases, the cells and containers must be washed out each time a test is made.